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AP Chemistry Unit 3 - Elements

AP Chemistry Unit 3 - Elements. Lesson 4 – Isotopes Book Section: 2.3. Isotopes. Isotopes are atoms of the same element with different masses. Isotopes have different numbers of neutrons. Atomic Mass.

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AP Chemistry Unit 3 - Elements

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  1. AP ChemistryUnit 3 - Elements Lesson 4 – Isotopes Book Section: 2.3

  2. Isotopes • Isotopes are atoms of the same element with different masses. • Isotopes have different numbers of neutrons.

  3. Atomic Mass • Atomic and moleculear masses can be measured with great accuracy with a mass spectrometer.

  4. Average Mass • Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations. • Average mass is calculated from the isotopes of an element weighted by their relative abundances.

  5. Sample Problem • Naturally occurring chlorine is 75.78% 35Cl, which has an atomic mass of 34.969 amu, and 24.22% 37Cl, which has an atomic mass of 36.966 amu. Calculate the average atomic mass (that is, atomic weight) of chlorine.

  6. Sample Problem • Naturally occurring chlorine is 75.78% 35Cl, which has an atomic mass of 34.969 amu, and 24.22% 37Cl, which has an atomic mass of 36.966 amu. Calculate the average atomic mass (that is, atomic weight) of chlorine. • 35.45 amu

  7. AP Problem • 1989 MC #24 • The mass of element Q found in 1.00 mole of each of four different compounds is 38.0 grams, 57.0 grams, 76.0 grams, and 114 grams, respectively. A possible atomic weight of Q is • 12.7 • 19.0 • 27.5 • 38.0 • 57.0

  8. AP Problem • 1989 MC #24 • The mass of element Q found in 1.00 mole of each of four different compounds is 38.0 grams, 57.0 grams, 76.0 grams, and 114 grams, respectively. A possible atomic weight of Q is • 12.7 • 19.0 – 64% correct, easy • 27.5 • 38.0 • 57.0

  9. AP Problem • 1984 MC #19 • Which of the following represents a pair of isotopes? Atomic Number Mass Number • I. 6 14 II. 7 14 • I. 6 7 II. 14 14 • I. 6 14 II. 14 28 • I. 7 13 II. 7 14 • I. 8 10 II. 16 20

  10. AP Problem • 1984 MC #19 • Which of the following represents a pair of isotopes? Atomic Number Mass Number • I. 6 14 II. 7 14 • I. 6 7 II. 14 14 • I. 6 14 II. 14 28 • I. 7 13 -- 87% correct II. 7 14 – very easy • I. 8 10 II. 16 20

  11. HW: 2.22, 2.24, 2.26, 2.28, 2.30, 2.32, 2.34 • This Week: • Tuesday – Periodic Table Structure (2.4, 7.1) • Wednesday – Quantitative Analysis of a Soluble Sulfate Day 2 • Thursday – Wave-Particle Duality (6.1, 6.2) • Friday – Gravimetric Analysis of a Chloride Salt Lab • 10/7 – Quantitative Analysis of a Soluble Sulfate Due • 10/18 – Gravimetric Analysis of a Chloride Salt Due • 10/20 – Elements Exam • 10/21 – Problem Set 2 Due

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